Gutsy Research: March 20, 2000   @Sea correspondent/ photographer, Tim Calver   Atol das Rocas, Brazil -- The moon has called us back to Atol das Rocas. The dramatic tides it brings to our temporary island laboratory cause ten feet of water to rush into the Rocas lagoon. Dr. Samuel Gruber, our expedition leader, is hoping that all of this extra swimming room will attract lots of sharks. A baby lemon shark is held by caring hands in the measuring trough. We followed our standard plan -- wait for high tide to bring sharks into Lama Lagoon (an offshoot of the main Rocas lagoon), string a net across Lama's entrance, and snare sharks as they leave the lagoon with the falling tide. Tonight our high tide happened just after five o'clock, and by 5:15 our nets were in the water. Sara Konigson carefully everts the stomach of a baby lemon shark. Maureen Kuenen supports the anesthetized shark on it's back while Dr. Rosa and Jessie Jenkins look on. With the shark held vertically, it is an easy matter to push the shark's stomach back into place. One by one, the sharks started hitting the net, the first one coming just as the moon cleared the cloudy horizon. We hoped to have the entire operation over in a little under two hours so we could avoid having to camp on the beach. A night under the stars is nice, but there is definitely something to be said for the hot meals and soft beds aboard our floating home, the Research Vessel SEWARD JOHNSON.   Brad Wetherbee, our expert shark tracker, predicted the rush of sharks almost to the minute. By seven, our team was running sharks from the water to the work-up area, and then back to the release area. Every shark we caught tonight was a re-capture from the last time we set our nets. The numbers from their implanted PIT tags were recorded in the book, and a handful were re-measured to compare with the initial measurements from two weeks ago. The difference between the two sets of measurements gives our researchers an idea of the statistical error in their measurements. We caught fifteen sharks tonight -- far fewer than last time.   The relaxed pace gave the stomach-eversion team a chance to go to work.   Lemon sharks have a natural ability to throw their stomach outside of their bodies. It's a technique they use to rid themselves of indigestible material like bones and shells. We use this ability to our advantage when we study what lemon sharks have been eating.

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A shark's dinner lies in the sampling tray. Removing these 20 cm long squid from the shark's stomach brought cheers from our crew and partially answered the question of what these shark's eat. Now, scientists will go to work determining what species of squid they are. Learn more about the sleek predator at the focus of Dr. Gruber's research efforts... Tim Calver is an accomplished underwater wildlife photographer and a veteran shark researcher in his own right. Click below to learn more... Under the supervision of Dr. Ricardo Rosa, the eversion team -- Maureen Kuenen, Jessie Jenkins, Bertran Feitoza and Sara Konigson -- lightly sedated one of their subjects. Then they held the shark upside-down. Maureen slid a long set of forceps in through the shark's open mouth, down its throat, and gently grasped the lining at the rear of the animal's stomach. With a slow series of pulls, Maureen brought the shark's stomach out of its mouth and carefully drooped the tender organ over his teeth. The stomach was empty...this little guy had not eaten recently. The team worked to carefully put his stomach back in its proper place, let him recover from the sedative, and sent him on his way. This is an invasive procedure, and seen from the perspective of a human with a firmly-anchored stomach, it takes a lot of faith in science to believe that such a dramatic rearrangement of anatomy is harmless. However, it is impossible to miss the care and concern that Dr. Rosa and his team show for these little sharks. It is a testament to their skill that not a single shark was injured during tonight's procedures.   In all, seven sharks had their stomach contents sampled. Four were completely empty...two had only small bits and pieces of gills and fins. These bits and pieces will provide hours of identifying work as researchers try to determine exactly what kind of fish they came from.   One shark gave the team a big surprise. As the stomach was beginning to show in the shark's throat, Maureen began to smile and said that she could see tentacles. When two relatively large squid plopped into the sampling pan, a small cheer erupted from the team. Finding an intact meal is exciting. But being able to count individual tentacles and look at the eye color of a recent meal truly fires the imagination. It makes you imagine the squid's final squirt at freedom...the shark zeroing in. Did he swallow these two squid in one mouthful? Maybe darted through a large school of squid and got lucky.   These two squid were a lucky find. Studying them -- maybe even finding out what they ate for their last meal -- will bring us a little closer to understanding the Atol das Rocas ecosystem and the world of the lemon shark. Anja Petersen escorts the first shark of the night from the gill net to the tagging area.

© 2000, Harbor Branch Oceanographic Institution